Shoulder (glenohumeral) dislocation is a common clinical presentation in the emergency department, comprising about 50 percent of all major joint dislocations.1 The large range of motion of the shoulder with minimal inferior tendinous support makes it prone to dislocation. Plain film radiography has been the imaging modality of choice for most clinicians when evaluating the ED patient with a suspected shoulder dislocation. Recent literature has demonstrated the superiority of point-of-care ultrasound (POCUS) in detecting both anterior and posterior shoulder dislocations, making it another rapidly evolving tool to improve accuracy, decrease error, and improve efficiency.2-4
Also, real-time ultrasonographic assessment of the articulation between the glenoid fossa and the humeral head is the ideal test when patients undergo procedural sedation for reduction. After shoulder manipulation, confirmation of the reduction attempt by plain film radiography incurs a delay that can prolong the length of stay. POCUS allows for a dynamic evaluation of the glenohumeral joint, immediately informing the clinician of a successful reduction or the need for additional shoulder manipulation without having to rely on plain film radiography.
The shoulder is composed of the bony articulation between the humeral head and the flat glenoid fossa that arises from the scapula. Anterior shoulder dislocations commonly occur when a large external force pushes the humeral head inferiorly below the glenoid fossa. Secondary contractions of the more powerful pectoralis and biceps muscles then pull the humeral head anteriorly, placing the humeral head just below the glenoid fossa or coracoid. Posterior shoulder dislocations are less common, representing only 2–5 percent of all dislocations, and are often missed during the initial patient presentation.5 Posterior shoulder dislocations are caused by forceful internal rotation and adduction of the shoulder, and classic mechanisms include seizures, trauma, and electrical shock. The posterior aspect of the shoulder is more stable than the anterior, making it less prone to dislocation. POCUS is an appealing and superior imaging alternative for the detection of both anterior and posterior dislocations.